Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

The title is probably horrible, but I couldn't think of a better sentence to describe what I'm attempting to do. I want to take the result of an equation made with 3 variables and then, with two of the variables, create the same number as if the third variable in the initial equation hadn't existed. Then, I want to find the percentage of each variable in the second equation. Once again, that was probably a terrible explanation, so here's an example.

result = a + b * c

That's the initial equation. Now plugging in numbers:

result = 1+2*3
result = 7

Now I want to be able to take 2 and 3 and make them add up to 7 somehow, then get the percentage of each in 7.

2/7=29%
3/7=43%

As you can see, this doesn't add up to 100%. I need it to add up to 100%, but I have no clue how. If more explanation is needed, just ask.

share|improve this question
2  
Vote to close as not a real question. No responses to the answers provided. –  Ross Millikan Jun 11 '11 at 4:53

2 Answers 2

More explanation is needed. Maybe one way to go is, I put forward a suggestion, you tell me why it's not what you want, that way maybe we get a clearer idea of what you want.

$7=2+2+3$, so the percentages of $2$ and $3$ in $7$ are $66$-and-two-thirds and $33$-and-one-third, respectively.

share|improve this answer
    
I don't understand how you came up with 66% & 33%, can you explain? It seems like what I'm trying to do (find 2 percentages that add up to 100 using) but I don't understand how you did that. Trying 2/(5-2) returns 40%. –  Jimmy May 12 '11 at 1:30
    
I used three numbers, and two out of three of them were $2$s, and one out of three of them was a $3$; so, two-thirds, which is to say, 66-and-two-thirds per cent, were $2$s, etc. But evidently this is not what you wanted, although I'm not sure I understand the answer you've given. –  Gerry Myerson May 12 '11 at 6:36

I found what I was looking for. A more compressed formula would be appreciated, though.

$b/(b+c)*100)/100*(a+b*c)$

$c/(b+c)*100)/100*(a+b*c)$

share|improve this answer
2  
You've a few unpaired parentheses... –  J. M. May 12 '11 at 2:37
1  
So your formula tells you the percentage of $2$s is $2/(5)100/100(7)$. I'm not sure how to parse this and get a number out of it. It's surely not $(2/500)/700=2/350000=1/175000$. Can it be $2/(500/700)$? That's $14/5$, and then the second number is $21/5$, and they don't add up to $100$. So before anyone can give a "more compressed formula," you had better show us how you think your formula works when $a=1$, $b=2$, and $c=3$. –  Gerry Myerson May 12 '11 at 6:42
    
The best I can parse this is to ignore the right parenthesis after the first $100$ and evaluate from left to right. Then the $100$s divide out and we have $\frac{b}{(b+c)(a+b*c)}$ and $\frac{c}{(b+c)(a+b*c)}$. Then $\frac{a}{a+b*c}+\frac{b}{(b+c)(a+b*c)}+\frac{c}{(b+c)(a+b*c)}=1$ but I don't know what to make of it. –  Ross Millikan Jun 11 '11 at 4:50

Your Answer

 
discard

By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.